Visitors to New Orleans who tire of the French Quarter and the Garden District can head some 20 miles west of the city to Destrehan, in St. Charles Parish, to view one of the oldest homes in Louisiana, a grand Greek Revival mansion dating to the late 18th century that once commanded farmland dedicated to the growing of indigo and sugar cane.

It’s listed on the National Register of Historic Places, which — at the risk of offending Rob Maness, the tea party Republican running for the U.S. Senate in Louisiana this fall — identifies it as Destrehan Plantation.

For Maness, apparently, “plantation” is the P-word. He was shocked — shocked! — when Bill Cassidy, the Baton Rouge congressman who is the favored Senate candidate of the state’s Republican establishment, deployed the P-word to describe the control over the Senate exercised by Majority Leader Harry Reid, a Democrat from Nevada. Reid, Cassidy told Environment & Energy News in an interview published last week, “runs the Senate like a plantation.”

To be sure, “plantation” carries some sinister associations, invoking the cotton (and indigo and sugar cane) fields of the antebellum South, worked by enslaved black Africans and their descendants. At Destrehan Plantation itself, according to its Wikepedia entry, the big house was built by six slaves under the direction of a free mulatto carpenter, whose payment included “one brute negro.”

So it came as no surprise that Reid took offense at Cassidy’s remark, with its implied comparison of Reid to a slave driver. Reid told reporters the comment was insensitive and that he deserved an apology. He likened Cassidy to Donald Sterling, the discredited former owner of the NBA’s Los Angeles Clippers who was forced to give up the team after the release of a recording of racially inflammatory statements he made.

But the reaction of Maness was more puzzling. He issued a news release brimming with outrage and calling for Cassidy to issue an immediate apology. In what may come as news to the folks who maintain the National Register, Maness declared that “the language he used included a term that is incredibly offensive to many Americans.”

Hmmm. If by “many Americans,” Maness means the 53 Democrats and two independents in the U.S. Senate who provide Reid the support that makes him arbiter of the Senate agenda, maybe so. Of course, one of those Democrats is Mary Landrieu, the three-term incumbent Maness and Cassidy are running to replace. Indeed, a main point made in Republican attacks on Landrieu is that her support for Reid and his left-wing policies works to the overall disadvantage of Louisiana, notwithstanding her claims to wield her clout for the state’s benefit. Republicans nationally in the fall election are focused on picking up the six Senate seats they need to replace Reid as majority leader with one of their own, and Landrieu, the lone remaining Democrat in statewide office in Louisiana, is at the top of their hit list.

Maness’ comments put him in league with Reid. Well, they say politics make strange bedfellows.

But of course, Maness’ objective is not to rush to the defense of Reid; it’s to take a shot at Cassidy (who, to his credit, has stood by his remark). In the Senate election, Maness’ only hope is to take votes away from his fellow Republican and finish ahead of Cassidy on Nov. 4, when all eight Senate candidates will appear together on the ballot. If, as projected, no candidate gets a majority of the votes Nov. 4, the top two finishers — expected to be Landrieu and a Republican — will meet in a runoff Dec. 6. Should Maness make the cut, he could spend a month bashing Landrieu for her solidarity with Reid.

That’s not likely to happen, based on polls of the race, which show Maness lagging well behind Cassidy and Landrieu. But Maness has raised enough money and attracted enough backing to establish a considerable degree of legitimacy and to distinguish himself from the five other candidates on the fringes of the race.

The main risk he poses for Cassidy, though, is that Maness’ supporters will be convinced by Maness’ arguments that Cassidy is not a real conservative and is part of the problem in Washington — and that they’ll stay home Dec. 6.

Greg Roberts is chief of The Advocate Washington bureau. His email address is groberts@the advocate.com. Follow him on Twitter, @GregRobertsDC.